This invention relates to a piezo-electric transformer comprising a piezo-electric body comprising a driving region equipped with input electrode means and at least one driven region equipped with output electrode means, said regions having opposite faces, at least one of the regions comprising a number of sections, said sections being polarized in a direction perpendicular to the opposite faces and one pole of each section being connected to an opposite pole of another section by electrically conductive means in such a way that the sections form a series arrangement.
The invention also relates to a circuit arrangement for operating a discharge lamp comprising such a piezo-electric transformer and to a circuit arrangement for igniting a high pressure discharge lamp comprising such a piezo-electric transformer.
A piezo-electric transformer as mentioned in the opening paragraph is known from Japanese Patent Application 06338642 A and from Japanese Patent Application 06234329. In the piezo-electric transformer disclosed in Japanese Patent Application 06338642 A the driving section comprises a series arrangement of polarized sections coupled with the input electrode means resulting in a relatively low input capacitance and therefore a relatively high input impedance. In the piezo-electric transformer disclosed in Japanese Patent Application 06234329 such a series arrangement is comprised in the driven region and coupled with the output electrode means so that the output impedance of the piezo-electric transformer is relatively high. In both piezo-electric transformers all the sections are polarized in the same direction. The poles of the sections are equipped with segments formed by patches of a metallic layer deposited on the opposite faces and connected to each other by means of external wiring. An important advantage of a relatively high impedance of the driving region is that the piezo-electric transformer becomes more suitable for use with an input voltage having a relatively high amplitude when the output power is very low or zero. A disadvantage of the known piezo-electric transformer is that its construction is relatively complicated and therefore expensive because of the external conduction wires, each of which connects two segments situated on different opposite faces.